Diaphragm heat treatment

[Calvin]

Hi,

so well then....google for DuPont or Mitsubishi and the type of film You want to use...say Mylar S. Download the Datasheet (2pages) and voila, on the very first page You´ll find a table ´Typical Values for Major Properties´ listing data for various film thicknesses. One of the fields says "Dimensional stability MD/TD,* % Shrinkage at 150°C (302°F) 30min". Man, that was difficult, eyhh?
And there´s too a general Product information sheet (6 pages) about Mylar, listing even more properties.
I wished all info I need were to find as easy as that.

About mechanical tension. If You just flatten out the film and glue it to the stator frame heating will increase mechanical tension by the shrinking action of the film. The value of mechanical tension remains rather low. Its easy to achieve considerably higher values of tension by mechanical stretching (up to 4% of length elongation with good films). If heat treatment is applied to such a high tensioned membrane stress is reliefed, but remains higher than that of a heat-treated-non-tensioned membrane.

jauu
Calvin

[bentoronto]

Originally Posted by Calvin

Hi,

so well then....google for DuPont or Mitsubishi and the type of film You want to use...say Mylar S. Download the Datasheet (2pages) and voila, on the very first page You´ll find a table ´Typical Values for Major Properties´ listing data for various film thicknesses. One of the fields says "Dimensional stability MD/TD,* % Shrinkage at 150°C (302°F) 30min". Man, that was difficult, eyhh?
And there´s too a general Product information sheet (6 pages) about Mylar, listing even more properties.
I wished all info I need were to find as easy as that.
snip

Was my question entirely stupid and was your reply profoundly clever? If so, then I would indeed deserve that kind of ridicule ("Man was that difficult, eyhh? :rolleyes"). Even supposing that my question was stupid, let's have a look at your answer.

(1) how many people have any idea what film is in the old panel they are holding in their hands that needs (maybe?) tightening? Even if they knew EXACTLY which of near-infinite number of generic and proprietary chemical compound names they should plug into Google, as you suggest, how do they know the spec sheet today matches or is helpful for dealing with their old panel and whatever treatments it has already had?

(2) how many people can make sense of unfamiliar jargon in a chemical spec sheet (to quote you, "Dimensional stability MD/TD") and are willing to proceed to possibly destroy their cherished Quad, Dayton-Wright, Martin Logan or other classic speakers based on these uncertainties? Even when some well-meaning source says something like "up to 4% of length elongation with good films" - does that mean length or width or area or both?

Not to mention, again, the challenges of waving an industrial heat gun at a panel and heating to not (much?) more than 150C. Perhaps the bottom line as you unconsciously demonstrate without humourous intent is that heat shrinking is risky. That might be the intelligent answer even if not an optimistic one.

I think that part of your answer was neither helpful nor funny to me. As I said, ridicule does have its place and when used in skilled hands. But thanks for trying.

[Calvin]

Hi,

reg1) is OT, because the whole thread is not about refurbishing, restretching or repairing panels but about the benefits of heat treatment to freshly built panels.
reg2) if one bothers in reading the Datasheet and Product information one would discover that terms like MD/TD are explained in an easy to understand way. If one is not entirely happy with the answers he/she can still ask Qs. But it´d show that he/she at least tried.

Apart from that, I won´t regard a Q ´entirely stupid´ and can comfortably live with ´profoundly clever´ ;-)

jauu
Calvin